Method of producing refined benzol



July 5, 1960 F. SONNTAG METHOD oF PRoDUcING REFINED BENzoL JONZm-m mDDmOMETHOD F PRODUCING REFINE!) BLENZOL Franz Sonntag, Dortmund-Mengede,Germany, assignor to Gelsenkirchener Bergwerks Akt-Ges., Essen, GermanyThe present invention relates to a method of producing refined benzol,and more particularly it relates to a method of producing rened benzolfrom coke oven gas containing crude benzol.

Several processes of refining a. crude. benzol obtained from coke ovengas are known; Recently severai methods have been published all of whichhave in common that they are based on a so-called catalytic refiningpressure hydrogenation. These latter methods are based on what has. beenproposed in the German Patent No. 550,123 to M. Pier. According4 tothese pressure refining processes, the crude benzol is vapor-ized atpressures exceeding 36'- atmospheres in a stream of pure hydrogen gas orin a: stream of free hydrogen-containing gas, and is then passed over acatalyst maintained at. a temperature of between 350 and 400 C. Thecatalyst consists of sulfides oi elements belonging to the sixth andeighth group of the periodic system and causes a cracking hydrogenationof the oxygen, nitrogen and sulfur bonds in the crude benzol, as well assaturation; of easily hydrogenizable unsaturated compounds. Aromaticconstituents of the crude benzol are not attacked, under the aboveconditions of refining hydrogenation.

These known processes of refining the crude benzolA contained in cokeoven gas have in common that the crude benzol has mst to be removed fromthe coke oven gas by a scrubbing process by absorption on activatedcarbon or by any other suitable process, and that the thus isolatedcrude benzol has then to be evaporated into a relatively small quantityof a free hydrogerbcontaining gas, prior to being passed over thecatalyst. Thus, the recovery and refining of crude benzol from coke ovengas is a multi-step high-pressure process requiring a relatively largeinvestment and involving considerable operating costs.

It is therefore an object of the present invention, to overcome theabove mentioned disadvantages in the production of refined crude benzolfrom coke oven gas.

It is another object of the present invention to devise a process forthe production of refined benzol from coke oven gas, which process maybe` carried out in a simple and economical manner. p

It is a further object of the present invention to provide a process forproducing refined benzol from coke oven gas,v without the addition ofhydrogen containing reducing gases other than those contained in cokeoven gas.

It isstill another object of the present invention to produce refinedbenzol from coke oven gas without requiring separation of crude benzolfrom the coke oven gas.

Other objects and advantages of the present invention willbecomeapparent from a further reading ofthe description and the appendedclaims. 70

With the above objects in View, the present' invention mainly comprisesin a method of producing refined benzol from ammonia-free coke oven gascontaining crude benzol, the steps of compressing the ammoniafree cokeoven gas, contacting the compressed gas with a sulfide catalyst so as topartially crack and hydrogenate the crude benzol contained in thecompressed gas, there by refining the crude benzol, and scrubbing `thethus treated gas with a Wash oil so as to form a solution consistingessentially of the refined benzol dissolved in the Wash oil.

According to a preferred embodiment, the present invention consists in amethod of producing refined crude benzol fromcoke oven gas containingcrude benzol, comprising the steps of freeing the colteV oven gas ofammonia, compressing and. heating the substantially ammomia-free cokeoven gas to a pressure of between about 13 and 16 atmospheres, andatemperature of between about 350 and 380 C., contacting the heated andcompressed crude benzol-containing ammonia-free coke oven gas with asulfide catalyst so as to at least partially crack and hydrogenate thecrude benzol contained in the com pressed coke oven gas, therebyrefiningthe crude benzol', scrubbing the thus treated gas with a fullyhydrogenated Wash oil so as to form a solution consisting essentially ofthe refined benzol dissolved in the WashV oil, and separating therefined benzol from the Wash oil.

Surprisingly it has been found that it is not necessary to remove fromthe: coke oven gas the crude benzol, which generally is present thereinin a quantity of about 25 grams per normal cubic: meter of coke ovengas, and to subsequently evaporate the crude benzol and mix the samewith a small quantity of a suitable gas before sub jectingthe crudebenzol to catalytic pressure refining.

According to the. present invention, two steps which were essentialaccording to the prior art processes, nameiy separation of the crudebenzol from the coke oven gas and subsequent evaporating and mixing oftheseparated crude benzol with a hydrogen containing gas can be omitted,and the crude benzol can be refined at relatively low overpressures.while still being contained in the coke oven gas. This is accomplishedby passing coke oven gas from which ammonia has been removed but whichstill` includes its oricinal contents of crude benzol, over any one cfthe suifide catalysts cenventionaily used for refining hydrogenation ofcrude benzol, whereby the temperature and pressure of the crudebenzol-containing, ammonia-free coke oven gas, as Well as: the period oftime for which the gas is to be in contact with the catalyst are to beso` adjusted as to achieve the desired refining effect.

Thus, according to a preferred embodiment of the present invention, thecoke oven gas after removal of tar and ammonia therefrom is compressedand` heated to the temperature of the catalyst and passes in thiscondition through the catalyst-containing vessel, in contact with thecatalyst, prior to removal of hydrogen sulfide and separation of therefined benzol from the gas. it depends primarily on the type of Washoil which is to be used whether removal of hydrogen sulfide is to` becarried out prior or after separation of the refined benzol from theremainder of the gas.

The novel features which are considered as characteristie for theinvention are set forth in particular' in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specic embodimentswhen read in connection with the accompanying drawing, in which thefigure is a schematic representation of the process of the presentinvention.

Referring now to the drawing, it may be seen that crude coke oven gasenters tar separator 2 as indicated by arrow 20. The gas then passesthrough ammonia washer 3 in countercurrent liow to water which isintroduced into the ammonia washer 3 as indicated by arrow 21. Asindicated by arrow 22, the gaswhich thus has been freed from tar andammonia passes through cornpressor 4 into condensate separator 5. Thegas then passes, as indicated by arrow 23, into preheater 6. Thecondensate which has been separated from the gas in condensate separator5 may be sprayed into preheater 6 as indicated by arrow 24. Frompreheater 6, the gas then passes as indicated by arrow 2S through heatexchanger S into catalyst chamber 7 in which contact is made between thecatalyst and the crude benzol contain- 'ing coke oven gas. From catalystchamber 7, the gas containing the now cracked and hydrogenated crudebenzol passes through heat exchanger 8, as indicated by arrow 26, andfrom there after giving ofi heat, the gas reaches benzol washer 9 asindicated by arrow 27. Between heat exchanger 8 and benzol washer 9, ahydrogen suliide remover of conventional construction (not shown in thedrawing) may be arranged. In benzol washer 9, the refined benzol isdissolved in wash oil and separated from the remainder of the coke ovengas. The gas passes from benzol washer 9 through gas puriiier 10 asindicated by arrows 28. The solution of refined benzol in wash oilleaves benzol washer 9 as indicated by .arrow 29 and passes throughexpansion valve 14 into benzol still 1.1. In benzol stillll, the renedbenzol is distilled-off and passes in Vapor form, as indicated by arrowto cooler12, and fromV there in `liquid form to stationary or movabletank `13. Y The wash oil frorrrwhich benzol has been distilled-olf inbenzol still 11 passesY from there through pump 15 into benzol washer 9,as indicated by arrow 31.

An installation such as described above is primarily designed for use inconnection with and adjacent to a central coking plant. In addition torefining crude benzol contained in the coke oven gases produced in thecentrol coking plant, the installation may also be employed for reiiningcrude benzol obtained in small coking units the capacity of which wouldnot warrant a separate installation as described above. In such smallCoking plants, the crude benzol may be washed out of the coke oven gasin conventional manner and transported to container 1 of the drawing.From container 1 crude benzol may be added, as indicated by arrows 32,to the ammonia free crude benzol-containing coke oven gasoriginatingfrom the central coking plant, preferably prior to introduction of thecoke oven gas into preheater'.

Thefollowing example is given as illustrative of the process of thepresent invention only, the present invention, however, not beinglimited to the specilic details of the example.

Example Crude coke oven gas from which ammonia has been removed 1spassed from the ammonia washer through a treated activated carbon.

one-stage compressor in which the gas is compressed to gas, is separatedfrom the compressed gas in condensate separator 5, and is introducedinto preheater 6 by means of a small injection pump (not shown in thedrawing). In preheater 6 such crude benzol condensate evaporates andbecomes again part of the gaseous mixture of crude benzol containingcoke oven gas.

'I'he coke oven gas leaving catalyst chamber 7 and containing reiinedbenzol, passes through a heat exchanger in which some of the heat of therefined benzol-containing gas is given off for heating crudebenzol-containing coke oven gas, prior to its introduction into thecatalyst chamber. Thereby a small portion of the retined benzol iscondensed. However, the major portion of the reined benzol is removedfrom the remainder of the coke oven gas by washing with a completelyhydrogenated wash oil such as Arsol-II-Fraction, dekalin or tetralin.`Generally, a wash oil incapable of forming resinous or gummy 'substancesshould be used. 'i n The coke oven gas coming from the ammonia washercontains 25.5 grams of crude benzol per normal cubic meter. f

The composition of the crude benzol contained in the coke oven gasentering the catalyst chambers is of approximately the followingcomposition:

Liquid vol- Bromine Boiling range, O. urne, percent Number g-l1`00 s Thecrude benzol is cracked and hydrogenated in the catalyst chamber andVthereby rened so that the coke oven gas leaving theV catalyst chambercontains rened benzol of approximately the following composition:V

Liquid Bromine Bolling range, O volume, N umher f percent g.l gf

57-70 1. 0 2.6 70-70.5 3.0 1. 2 70.579.5 1.0 0.27 79.5-80.5 67. 0 0. 05S05-109.5 1.0 0. 58 109.5- 13. 0 0.' 10 110.5-123 0. 0.5 0.10 123.0-1235 4. 5 0. 22 123.5-138 0--.- 0.5 0. 26 138.0-138 5 3 4. 0 0.65 138.5*2003. o 2. q,

1 Benzene. 2 Toluene. I Xylene.

The catalyst employed 1n catalyst chambers 7 was produced in customarymanner by imbibing activated car` bon with a solution of molybdenumoxide and'cobalt nitrate in ammonia, and subsequent drying of the thusThe thus prepared catalyst becomes fully effective only in an atmospherecontainin large quantities of hydrogen sulfide. Y

As stated above, all of the sulfide catalysts customarily used forrefining crude benzol may be used in accordance with' the presentinvention preferably sulides of chro'- mium, molybdenum or tungstenwhich are deposited on carriers such as aluminium oxyde, pumice,activated carbon or clay. These suldes may also contain as promoterssmall amounts of ferrie, nickelor cobalt sultide.Y p Such catalystsunder the selected process conditions cause an effective reining of thecrude benzol. Such catalysts are traded ready for use and are describedfor instance in Petroleum Processing, August 1955', pp. 1174, lines141i, p. 1188, left side, p. 1190 left side, p'. 1194 left side, and inthe German Patent 665,228 as well as in various newer patents. l Thebest result was reached with a catalyst which contained about 10% Mo and1% Co in sulfide form de# posited on carbon of commercial qualityobtained .by

gas adsorption. Y .l However the process does not depend on usingaparticular catalyst but a main condition is that the gas contains about5 to 15 grams HES per cubic meter.

Prior to removing the refined benzol from the remainder of the coke ovengas, it is preferred according to the present invention to remove fromthe gas hydrogen sulfide which usually is present in a quantity of about15 grams per normal cubic meter of gas leaving the catalyst chambers.Removal of hydrogen sulde from the gas may `be carried yout in anyconventional manner such as is described, for instance, in Gluud and D.L. Jacobson International Handbook Aof the By-product Coke Industry, NewYork 1932, Chapter 9, pp. S33-583.

Preferably, the coke oven gas containing the crude benzol is subjectedto catalytic treatment at a pressure of :between and 30 atmospheres anda temperature of between 300 and 450 C., and most preferably thecatalytic treatment is carried out at a pressure of between 13 and 116atmospheres and at a temperature of between 350 and 380 C.

The coke oven gas remaining after removal of refined benzol and hydrogensulfide is, if desired, further puriiied prior to lbeing pumped intopipes `for long-distance gas supply.

The small portion of refined benzol which is condensed in heat exchanger8 may be combined with the major portion of rened benzol which has beendistilledoil? from the wash oil, and the entire thus refined benzol maybe either used as motor fuel or may be further fractionated into itsconstituents such as benzene, toluene, xylene, etc.

Without further analysis, the foregoing will so fully reveal the `gistof the present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to ybecomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of producing re'ned benzol lfrom coke oven gas containingcrude benzol, comprising the steps of removing ammonia from said cokeoven gas; compressing and heating the thus formed substantiallyammonia-free coke oven gas to a pressure of between about 5 and 30atmospheres and a temperature of between about 300 and 450 C.;contacting said heated and compressed substantially ammonia-free cokeoven gas with a sulde catalyst so as to at least partially crack andhydrogenate the crude benzol contained in said compressed coke oven gas,thereby reining said crude benzol; and scrubbing the thus treated gaswith a Wash oil free of gum-forming constituents so as to form asolution consisting essentially of said refined benzol dissolved in saidwash oil.

2. A method of producing refined benzol from coke oven gas containingcrude benzol, comprising the steps of removing ammonia from said cokeoven gas; compressing and heating the thus formed substantiallyammonia-free coke oven gas to a pressure of between about 13 and 16atmospheres and a temperature of between about 350 and 380 C.;contacting said heated and compressed substantially ammonia-free cokeoven gas with a sulfide catalyst so as to at least partially crack and.

hydrogenate the crude benzol contained in said compressed coke oven gas,thereby rening said crude benzol; and scrubbing the thus treated gaswith a wash oil free of gum-forming constituents so as to form asolution consisting essentially of said relined benzol dissolved in saidwash oil.

3. A method of producing rened benzol from coke oven gas containingcrude benzol, comprising the steps of freeing said coke oven gas ofammonia; compressing and heating the substantially ammonia-free cokeoven gas to a pressure of between about 13 and 16 atmospheres and atemperature of between about 350 and 380 C.; contacting said heated andcompressed crude benzol-containing ammonia-free coke oven gas with asulfide catalyst so as to at least partially crack and hydrogenate saidcrude `benzol contained in said compressed coke oven gas, thereby reningsaid crude benzol; scrubbing the thus treated gas with a fullyhydrogenated wash oil so as to form `a solution consisting essentiallyof said refined benzol dissolved in said Wash oil; and separating saidrefined benzol from said wash oil.

References Cited in the file of this patent FOREIGN PATENTS 11,202.Great Britain Aug. 12, 1884 16,493 Great Britain Aug. 15, 1913 345,738Great Britain Apr. 2, 1931

1. A METHOD OF PRODUCING REFINED BENZOL FROM COKE OVEN GAS CONTAININGCRUDE BENZOL, COMPRISING THE STEPS OF REMOVING AMMONIA FROM SAID COKEOVEN GAS, COMPRESSING AND HEATING THE THUS FORMED SUBSTANTIALLYAMMONIA-FREE COKE OVEN GAO TO A PRESSURE OF BETWEEN ABOUT 5 AND 30ATMOSPHERES AND A TEMPERATURE OF BETWEEN ABOUT 300* AND 450*C.,CONTACTING SAID HEATED AND COMPRESSED SUBSTANTIALLY AMMONIA-FREE COKEOVEN GAS WITH A SULFIDE CATALYST SO AS TO AT LEAST PARTIALLY CRACK ANDHYDROGENATE THE CRUDE BENZOL CONTAINED IN SAID COMPRESSED COKE OVEN GAS,THEREBY REFINING SAID CRUDE COMPRESSED SCRUBBING THE THUS TREATED GASWITH A WASH OIL FREE OF GUM-FORMING CONSTITUTENTS SO AS TO FORM ASOLUTION CONSISTING ESSENTIALLY OF SAID REFINED BENZOL DISSOLVED IN SAIDWASH OIL.